1. Field
The present invention relates to a method and an apparatus for auto focusing, and, more particularly, to a method and apparatus for auto focusing that calculates the focal distance on the basis of a blur level of an image and corrects a method of calculating the focal distance when an image that is captured at the calculated focal distance is out of focus.
2. Description of the Related Art
Efforts have been made to improve the quality of images in image-capturing apparatuses, such as digital cameras and digital camcorders, which are widely used, by using an auto focusing function.
In general, the image-capturing apparatus, such as a camcorder or a camera, performs photoelectric conversion, that is, converts optical signals that are incident on a lens into electric signals, and performs predetermined image processing on the converted image signals to form an image.
Auto focus and a manual focusing are methods of adjusting the focus of the image-capturing apparatus. According to auto focusing technology, a subject is detected using image signals of the subject that is captured by a lens, and a focal lens is automatically driven according to the subject, such that the focus of the image-capturing device is automatically adjusted.
In order to adjust the focus of the image-capturing apparatus, in general, the focal lens is moved to capture an image that is in complete focus. In this case, images that are out of focus need to be captured, which requires a lot of time, leading to shutter lag.
In order to solve this problem, methods of finding the position of a focal lens where an image is in focus by using two or three images that are out of focus have been proposed.
According to most of the methods, image data is acquired from the images that are captured at different distances, data to determine the position of the focal lens is obtained from the acquired image data, and the obtained data is stored in an image-capturing apparatus in the form of a look up table (LUT).
In a method of storing data in the form of a look up table (LUT), which is used to determine the position of the focal lens, in the image-capturing apparatus as the auto focusing method for the image-capturing apparatus, it is difficult to store all of data in the form of a LUT. As a result, if data that is not included in the LUT stored in the image-capturing apparatus is input, an error occurs.